mke2fs: fix check for absurdly large devices

The check in mke2fs is intended to be for the number of blocks in the
filesystem exceeding the maximum number of addressable blocks in 2^32
bitmaps, which is (2^32 * 8 bits/byte * blocksize) = 2^47 blocks,
or 2^59 bytes = 512PiB for the common 4KiB blocksize.

However, s_log_blocksize holds log2(blocksize_in_kb), so the current
calculation is a factor of 2^10 too small.  This caused mke2fs to fail
while trying to format a 900TB filesystem.

Fixes: 101ef2e93c25 ("mke2fs: Avoid crashes / infinite loops for absurdly large devices")
Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 9152360..0ba2bf3 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2183,9 +2183,11 @@ profile_error:
        }
        /*
         * Guard against group descriptor count overflowing... Mostly to avoid
-        * strange results for absurdly large devices.
+        * strange results for absurdly large devices.  This is in log2:
+        * (blocksize) * (bits per byte) * (maximum number of block groups)
         */
-       if (fs_blocks_count > ((1ULL << (fs_param.s_log_block_size + 3 + 32)) - 1)) {
+       if (fs_blocks_count >
+           (1ULL << (EXT2_BLOCK_SIZE_BITS(&fs_param) + 3 + 32)) - 1) {
                fprintf(stderr, _("%s: Size of device (0x%llx blocks) %s "
                                  "too big to create\n\t"
                                  "a filesystem using a blocksize of %d.\n"),